The present invention relates to a safety belt buckle for receiving and locking an insertion tongue; the safety belt buckle has a housing with an insertion slot for the insertion tongue with a spring-loaded ejector arranged in the insertion slot, a latch that is arranged within the safety belt buckle and cooperates with a cutout of the insertion tongue in a locking position, with the latch holding the insertion tongue in a coordinated recess of the safety belt buckle, and a spring-loaded sliding key that is guided transverse to a plane of movement of the latch for cancelling the locking position, whereby a securing element is movably arranged within the housing which, in the locking position of the safety belt buckle, fixes and secures the latch and is movable by the sliding key into a releasing position of the latch for releasing the safety belt buckle.
A safety belt buckle of the aforementioned kind is described in DE-OS 27 19 325. In this known safety belt buckle, the latch, which is disposed in the safety belt buckle housing and has a tendency to open by itself is secured by a securing element which is arranged in the plane of the sliding key and is movable in the same direction as the sliding key so that the latch is secured in a position in which it locks the insertion tongue. When releasing the safety belt buckle the sliding key with coordinated abutments first moves the securing element into a releasing position for the latch so that the latch opens and releases the insertion tongue while simultaneously releasing the safety belt buckle.
The safety belt buckle of the aforementioned kind ha the disadvantage that the safety belt buckle is not protected against shock-type acceleration forces occurring especially in the plane of the sliding key movement, such forces, for example, occurring when the safety belt buckle is moved in its longitudinal direction in the course of a tightening step of the safety belt during an accident. When during the course of such a tightening movement the safety belt buckle at the end of the tightening movement is suddenly stopped, then the sliding key, due to its own mass inertia, continues the movement in the tightening direction so that the sliding key and the housing of the safety belt buckle perform a movement relative to one another with which the sliding key is inserted into the safety belt buckle and moves the securing element into the releasing position of the latch. Thus, with the aforementioned safety belt buckle, a self-opening of the safety belt buckle is possible in the course of a tightening movement acting on the safety belt buckle.
It is therefore an object of the invention to improve a safety belt buckle of the aforementioned kind such that it is shock-protected against acceleration forces in the actuating direction of the sliding key.